Various studies utilizing laser light scattering have been undertaken, some in direct support of biomedical research being performed at NIH and similar institutions, others as part of a long-term technical development program. Recent emphasis has been on developing methods to probe phase transitions in lipid-water systems and on developing theories for interpreting measurements made with laser-Doppler blood flow instrumentation. Instrumentation was developed to probe thermal transitions of solutions that contain phospholipid vesicles. Measurements have been made of the properties of dilute aqueous dispersions of dimyristoyl phosphatidyl glycerol, and results have been correlated with previously acquired data on surface films formed from the same materials. Morphological transitions which occur at temperatures above the main "gel-liquid crystal" transition temperatures have been established. Analytical theory and computer-based Monte-Carlo calculations have been used to extend a previously developed model for describing the interaction of photons with blood cells moving in the peripheral microvasculature. A diffusion model was used to determine the path length distributions of photons moving within biological tissue, and properties of surface emitted light have been investigated. Using a previously devised scheme involving dynamic light scattering to study the gelation and elasticity of polymer networks, measurements were performed to relate mechanical relaxation of networks to their topological and molecular structure. Studies of gelation kinetics have been initiated.